Deployment of threat agents poses significant threats to both human and economic heath. This threat is compounded by a limited ability to detect deployment of the agents. Prior art detection strategies rely on separate instrumentation for detection and identification of the threat agent. Conventional means of detecting airborne matter include relatively non-specific optical and spectroscopic methods, including laser scattering, ultraviolet laser induced fluorescence (UV-LIF) and laser induced breakdown spectroscopy (LIBS). Conventional means to identify a threat agent include wet chemical methods or spectroscopic methods. Reagent-based identification of biological threat agents includes methods such as specific antibodies, genetic markers and propagation in culture. While highly specific, these identification methods are time-consuming, labor-intensive and costly. Spectroscopic means, for identification, provide an alternative to reagent-based identification methods and include mass spectrometry, infrared spectroscopy, Raman spectroscopy, and imaging spectrometry. Mass spectrometry is limited by sensitivity to background interference. Infrared spectroscopy exhibits low sensitivity. Raman spectroscopy can be implemented in several different configurations, including normal Raman spectroscopy, UV resonance Raman spectroscopy, surface enhanced Raman spectroscopy (SERS) and non-linear Raman spectroscopy. While normal Raman spectroscopy has demonstrated adequate sensitivity and specificity for detection of airborne matter, other forms of Raman spectroscopy suffer from inadequate sensitivity, specificity or signature robustness. Prior art imaging spectroscopy is limited by the need to switch from a broad band light source, for optical imaging, to a substantially monochromatic light source for spectroscopic imaging. This results in a signification time period between detection and identification during which time the sample may degrade.
The present disclosure describes a reagent free sensor using Raman spectroscopy and Raman imaging spectroscopy to detect and identify a sample simultaneous with sample deposition. The system and methods of the present disclosure may operate in either a trigger mode or an identification mode. The present disclosure describes an approach that reduces system and method complexity by using a single illumination source.